JP3284796B2 - Airbag device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airbag apparatus in which surplus power of an ignition system backup power supply is supplied to a control system backup power supply so that the control for deploying an airbag can be completed satisfactorily.

[0002]

2. Description of the Related Art An airbag device 1 shown in FIG. 3 is mounted on a vehicle to deploy an airbag that protects an occupant from an impact in the event of a vehicle collision, and is a detonating element called a squib that is an airbag deployment trigger. By igniting and exploding 2d and 2p, the airbag inflated by the gas pressure is inflated between the occupant and the steering wheel or the dashboard, and functions to cushion the impact applied to the occupant. The airbag device 1 receives an ignition command when a collision occurs, and supplies an ignition current from the battery power supply 3 to the detonating elements 2d and 2p to cause ignition and detonation. And a control circuit 5 for issuing an ignition command together with the collision determination.

The ignition circuit 4 grounds a pair of detonating elements 2d and 2p corresponding to the airbags on the driver's seat side and the passenger's seat side via switching elements Qd and Qp which are closed in response to an ignition command. , Tide D for wraparound prevention
The shock sensor 6 is commonly connected via d and Dp, and the shock sensor 6 is further connected to the battery power supply 3 via a diode Dc and an ignition switch 7. The shock sensor 6 is constituted by a switch that detects and closes mechanically when a shock is applied, and ignites the detonating elements 2d and 2p in response to an ignition command issued by the control circuit 5 erroneously despite no impact. It is provided for the purpose of not letting it. While the shock sensor 6 is provided to prevent runaway of the control circuit 5, the switching element 2
For example, d and 2p have a function of preventing the deployment of the airbag when the impact sensor 6 is closed with a small impact such as when the vehicle rides on the shoulder of the road.

The control circuit 5 boosts the output voltage of the battery power supply 3 to a rated voltage when the output voltage falls below the rated voltage, and outputs the boosted circuit 8 by controlling the output of the boosted circuit 8 to a constant voltage. And a non-volatile memory 12 for writing and storing data used in the collision determination, and the like. The booster circuit 8 is connected to a conduction path extending from the ignition switch 7 via a diode Ds, and has a rated voltage of 12V.
Assuming a case where the output battery power supply 3 drops to about 5 V according to the load condition, the same voltage is output for an input voltage exceeding 12 V, but a constant voltage of 12 V is output for an input voltage of 12 V or less. It works to realize the input / output characteristics. Specifically, for example, a ground between a choke coil and a downstream rectifier circuit of a pair of rectifier / smoothing circuits opposed to each other with a choke coil therebetween is grounded via a PWM control transistor, and the transistor is turned on / off so that the boosted output maintains a constant value. -A configuration in which the duty is variably controlled is used. Further, as the constant voltage circuit 9, for example, a three-terminal regulator is used, and its configuration is such that a divided output of the output voltage of the transistor connected between the input and output terminals is compared with a reference voltage in an error amplifier, and the error voltage is adjusted. This is very common in which the output of the error amplifier is fed back to the transistor so that the output becomes zero. The collision determination circuit 11 processes the output of the acceleration sensor 10 according to a predetermined arithmetic algorithm, and makes a collision determination when the strength of impact and the amount of change in speed exceed predetermined threshold values, respectively, and switches the switching elements Qd and Qp. Supply a closing signal to the The collision determination circuit 11
Is responsible for writing the collision data obtained before and after the deployment of the airbag into the nonvolatile memory 12 in order to save the data used for collision determination, that is, the collision data, for post-mortem analysis. It is as important as judgment. As the nonvolatile memory 12, for example, an EEPROM or the like is used.

By the way, in order to cope with an unexpected situation in which a current path extending from the battery power source 3 to the ignition circuit 4 or the control circuit 5 is cut off upon occurrence of a collision, an ignition circuit 4 is provided.
And the control circuit 5 have backup power supplies 14 and 15 respectively.
Is attached. The ignition system backup power supply 14 is configured by branch-connecting a capacitor Ca to a current path between the diode Dc and the shock sensor 6 through a parallel connection circuit of a charging resistor Ra and a discharging diode Da. A detonating element 2d in place of the battery power source 3 in the accident,
It functions to supply an ignition current to 2p. On the other hand, the control system backup power supply 15 is configured by branch-connecting a capacitor Cb to a current path between the booster circuit 8 and the constant voltage circuit 9 via a parallel connection circuit of a charging resistor Rb and a discharging diode Db. In addition, it functions to supply a power supply current to the collision determination circuit 11 via the constant voltage circuit 9 instead of the battery power supply 3 that has suffered the interruption accident.

[0006]

In the above-described conventional airbag apparatus 1, the ignition system backup power supply 14 and the control system backup power supply 15 are completely independent, and therefore, if a collision occurs, the battery power supply 3 is cut off. In a case where the airbag must be deployed only by using the backup power supplies 14 and 15 for a period required for ignition and detonation of the detonating elements 2d and 2p, for example, a period of about 2 ms. After the completion of the supply of the ignition current, the capacitor Ca of the ignition system backup power supply 14 is usually left with a sufficient current supply capacity. However, as described above, the control system backup power supply 15 has a task of writing collision data related to the collision to the nonvolatile memory 12 after making a collision determination in accordance with a predetermined arithmetic algorithm and further performing post collision analysis. In addition, the nonvolatile memory 12 such as an EEPROM requires a considerably long time to write data as compared with a general RAM or the like which can perform writing and reading at any time.
If the terminal voltage drops below the reset voltage of the collision determination circuit 11 at an early stage, the collision data may not be completely written in some cases.
In particular, when a time of about 30 ms elapses from the occurrence of a collision until a collision is determined due to a slow collision, the voltage drop of the capacitor Cb is reduced by the time of writing the collision data. There is a problem that the writing of collision data is apt to occur due to considerable progress.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and receives an ignition command when a collision occurs, and applies an ignition current from a battery power supply to a detonating element which is a deployment trigger of an airbag to ignite. An ignition circuit to be detonated, a control circuit that is energized by the battery power source, makes a collision determination according to a predetermined arithmetic algorithm, and issues the ignition command together with the collision determination, and is provided in each of the control circuit and the ignition circuit; The control system backup power supply and the ignition system backup power supply, which are alternative power supplies when the battery power supply is shut off, are switched in response to a switching command issued by the control circuit following the ignition command, and the ignition system backup power supply is changed to the control system backup power supply. And a switch circuit for connection.

The present invention also provides that the control circuit issues the ignition command to the ignition circuit and then issues the switching instruction at a point in time when a time required for ignition and detonation of the detonating element has elapsed. A circuit is connected to the battery power supply in series with a detonating element that is energized by an ignition current, ignites and detonates, an impact detection sensor that detects and closes an impact, and a switching element that is closed in response to an ignition command. The system backup power supply is formed by branch-connecting a charge / discharge circuit in which a capacitor is connected in series with a parallel connection circuit of a charging resistor and a discharge diode to an energizing path connecting the battery power supply and the ignition circuit, and a control circuit. Is connected to a battery power supply, and when the output voltage of the battery power supply falls below the rated voltage, the voltage is boosted to the rated voltage and output. A constant voltage circuit for controlling the output of the booster circuit to a constant voltage and outputting the same; a collision determination circuit supplied with power from the constant voltage circuit and performing collision determination based on an acceleration signal; A non-volatile memory connected to the circuit for writing and storing data used for collision determination, and a control system backup power supply is provided on a current path connecting the booster circuit and the constant voltage circuit to a charging resistor and a discharging diode. Another feature is that a charging / discharging circuit in which a capacitor is connected in series is branched and connected to the parallel connection circuit.

[0009]

According to the present invention, a control system backup which becomes an alternative power supply when a battery power supply is cut off is provided in a control circuit for issuing an ignition command by making a collision determination and an ignition circuit for supplying an ignition current to the detonating element in response to the ignition command. A power supply and an ignition system backup power source are provided, respectively, and a switch circuit that switches in response to a switching command issued by the control circuit following the ignition command connects the ignition system backup power source to the control system backup power source, thereby providing the ignition system backup power source. Surplus power is supplied to the control system backup power supply so that the airbag deployment control can be completed well to the end, including the storage of collision data.

[0010]

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an embodiment of the airbag device of the present invention, and FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG.

An airbag apparatus 21 shown in FIG. 1 connects an ignition backup power supply 14 and a control backup power supply 15 as an alternative power supply when the battery power supply 3 is cut off, via a switch circuit 22, and a control circuit. 5, the switch circuit 22 is switched by a switch command issued following the ignition command, so that current is supplied from the ignition system backup power supply 14 to the control system backup power supply 15. The switch circuit 22 is a combination of a transistor Q1 that is turned on by receiving a switching command from the collision determination circuit 11 and a transistor Q2 that is turned on when the base is grounded by the transistor Q1. Immediately after issuing an ignition command having a pulse width of several ms to the switching elements Qd and Qp in the circuit 4, the transistor Q1 is turned on to switch the switch circuit 22, and at the same time, the storage of collision data is started.

For example, at time t shown in FIGS.
0, a collision occurs, and almost at the same time, the battery power supply 3 is cut off, and the ignition circuit 4 and the control circuit 5
However, assume that a situation has arisen in which both must rely on the backup power supplies 14 and 16. In this case, the collision determination circuit 11 in the control circuit 5 makes a collision determination at time t1 according to a predetermined calculation algorithm, issues an ignition command having a pulse width of several ms, and then issues a switching command at the falling edge of the ignition command. Emit. Therefore, as shown in FIG. 2D, the switch circuit 22 is closed at time t2. As a result, the ignition system backup power supply 14, which has finished its task together with the ignition and detonation of the detonating elements 2 d and 2 p, is switched to the switch circuit 22.
Is connected to the control system backup power supply 15, and the electric charge remaining in the capacitor Ca of the ignition system backup power supply 14 is supplied to the constant voltage circuit 9 via the switch circuit 22. In this case, the constant voltage circuit 9 includes the backup power supply 1
Since the capacitors Ca and Cb, which are the main components of the control circuits 4 and 15, are connected in parallel, the control system backup power supply 15, which has dropped to about 7V, for example, apparently recovers to about 9V. The surplus power for energizing the collision determination circuit 11 can be dramatically increased.

Thus, for example, when a slow collision occurs, for example, from the time t0 when the collision actually occurs to the time t1 when the ignition command is issued, the ignition command is often used in the related art. In some cases, the output voltage of the control system backup power supply 15 at the time of the occurrence of the power failure drops to near the reset voltage, which is the minimum operation guarantee voltage of the collision determination circuit 11. With the assistance of the system backup power supply 14, the control system backup power supply 15 can reliably supply the power supply voltage equal to or higher than the minimum operation guarantee voltage until the collision determination circuit 11 finishes writing the collision data in the nonvolatile memory 12. . The time ΔT shown in FIG. 2 (E) indicates the difference between the duration of the minimum operation guarantee voltage when no assistance is provided by the ignition system backup power supply 14 and when the assistance is provided. In this case, it takes more time to write data than in a RAM or the like, and a margin for writing to a nonvolatile memory 12 such as an EEPROM is provided.

As described above, according to the airbag apparatus 21, after the ignition elements 2d and 2p are ignited, the current supply target is lost. By supporting the backup power supply 15, both the effective use of the ignition backup power supply 14 and the support of the backup power supply of the control backup power supply 15 are possible, and it is ensured that the collision data is stored until the airbag is deployed. It can be. In addition, the airbag device 21 activates the ignition-system backup power supply 14 when the ignition element 2d, 2p that ignites and detonates when the required ignition energy is applied elapses a time that exceeds the energizing time of the ignition current leading to the ignition and detonation. Since power is supplied to the control system backup power supply 15 from the start, the ignition elements 2d and 2p can be reliably ignited and exploded, and the remaining electric power can be used effectively.

Further, even if the energization path connecting the battery power supply 3 and the ignition circuit 4 is cut off with the occurrence of a collision, the airbag device 21 keeps the ignition system backup power supply 14 charged before the occurrence of the collision. Can supply an ignition current to the ignition circuit 4 in place of the battery power supply 3,
As a result, the ignition elements 2d and 2p can be reliably fired, and the ignition circuit 4 operates only when both the impact sensor 6 and the switching elements Qd and Qp are closed. In spite of the fact that the airbag is deployed by the impact or the impact command is erroneously issued from the control circuit 5 in spite of the fact that the airbag is not subjected to the impact, the detonating elements 2d and 2p are ignited and detonated. Can be prevented. In addition, the airbag device 2
1 is a collision determination circuit 11 based on the output voltage of the battery power supply 3 controlled in two stages by the booster circuit 8 and the constant voltage circuit 9.
Can be operated stably, and the control system backup power supply 15 continues to operate the collision determination circuit 11 by receiving the power supply from the ignition system backup power supply 14 after the ignition and detonation of the detonating elements 2d and 2p. It is possible to reliably write the data that has resulted in the collision, that is, the collision data, in the nonvolatile memory 12.

[0016]

As described above, according to the present invention,
A control circuit that issues a firing instruction by making a collision determination and an ignition circuit that receives an ignition command and supplies an ignition current to the detonating element,
A control system backup power supply and an ignition system backup power supply are provided respectively as alternative power supplies when the battery power is cut off. After the ignition element is ignited, the current is not supplied after the ignition element is ignited.The power remaining in the ignition system backup power supply is supplied to the control system backup power supply after the ignition is initiated, so that the ignition system backup is provided. Both effective use of the power supply and support of the backup capacity of the control system backup power supply are possible, and it is possible to ensure that the collision data is stored until the airbag is deployed. A slow collision that took some time before the ignition command was issued When such a voltage control engagement backup power supply at the time of issuing the ignition command, even though dropped to minimum operation assurance voltage at which the reset voltage close to the control circuit, assisted by ignition system backup power supply,
The control system backup power supply has excellent effects such as being able to reliably supply a power supply voltage equal to or higher than the minimum operation guarantee voltage until the collision data is completely written in the nonvolatile memory.

Further, according to the present invention, since the control circuit issues an ignition command to the ignition circuit and then issues the switching command at a point in time when a required time for the ignition and detonation of the detonating element has elapsed, For the detonating element that ignites and detonates when the required ignition energy is given, it is possible to supply power from the ignition-system backup power supply to the control-system backup power supply after energizing the ignition current for the time until the ignition and detonation. As a result, the ignition element is reliably fired,
In addition, there is an effect that the remaining power can be effectively used.

Further, according to the present invention, even if the power supply path connecting the battery power supply and the ignition circuit is cut off with the occurrence of the collision, the ignition system backup power supply charged before the collision occurs replaces the battery power supply. The ignition circuit can supply an ignition current to the ignition circuit, thereby making it possible to reliably ignite the ignition element, and since the ignition circuit operates only when both the impact sensor and the switching element are closed, the roadside Accidents such as the deployment of the airbag due to the impact of getting on the vehicle, or the ignition element being ignited and detonated by the ignition command issued by the control circuit erroneously, even though the airbag was not impacted. And the like.

Further, according to the present invention, the collision judging circuit can be operated stably by the output voltage of the battery power supply controlled in two stages by the booster circuit and the constant voltage circuit, and the control system backup power supply ignites the detonating element. Since the collision determination circuit is continuously operated by receiving the power supply from the ignition system backup power supply after the detonation, it is possible to reliably write the data that led to the collision determination, that is, the collision data, to the nonvolatile memory. .

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of an airbag device of the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG. 1;

FIG. 3 is a circuit configuration diagram showing an example of a conventional airbag device.

[Explanation of symbols]

 2d, 2p Explosive element 3 Battery power supply 4 Ignition circuit 5 Control circuit 6 Shock sensor 8 Boost circuit 9 Constant voltage circuit 10 Acceleration sensor 11 Collision determination circuit 12 Nonvolatile memory 14 Ignition system backup power supply 15 Control system backup power supply 21 Airbag device 22 Switch circuit Qd, Qp Switching element Ra, Rb Charge resistance Da, Db Discharge diode Ca, Cb Capacitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60R 21/32

Claims (4)

(57) [Claims] An ignition circuit which receives an ignition command when a collision occurs, applies an ignition current from a battery power supply to a detonation element which is a deployment trigger of an airbag, and ignites the ignition. A control circuit for issuing the ignition command together with the collision determination, and a control system backup power supply and an ignition system which are provided in the control circuit and the ignition circuit, respectively, and serve as alternative power supplies when the battery power is cut off. An airbag apparatus, comprising: a backup power supply; and a switch circuit that is switched in response to a switching command issued by the control circuit following an ignition command and connects the ignition system backup power supply to the control system backup power supply. 2. The control circuit according to claim 1, wherein after issuing an ignition command to the ignition circuit, the switching command is issued at a point in time when a time required for ignition and detonation of the detonating element has elapsed. 2. The airbag device according to 1. 3. The battery circuit according to claim 1, wherein the ignition circuit includes: an ignition element that is energized by an ignition current to initiate ignition; an impact detection sensor that detects and closes an impact and a switching element that is closed by receiving an ignition command; The ignition system backup power supply is connected in series to a current path connecting the battery power supply and the ignition circuit, and a charging / discharging circuit in which a capacitor is connected in series to a parallel connection circuit of a charging resistor and a discharging diode is branched and connected. The airbag device according to claim 1, wherein the airbag device comprises: 4. A booster circuit connected to a battery power supply, wherein the control circuit boosts the output voltage to a rated voltage when the output voltage of the battery power supply falls below a rated voltage, and outputs the boosted circuit.
A constant voltage circuit which is connected to the booster circuit and controls the output of the booster circuit to step down to a constant voltage and outputs the same; a collision determination circuit which is supplied with power from the constant voltage circuit and makes a collision determination based on an acceleration signal; A nonvolatile memory connected to the collision determination circuit for writing and storing data used for the collision determination, and wherein the control system backup power supply is configured to charge a current path connecting the booster circuit and the constant voltage circuit. 2. The airbag device according to claim 1, wherein a charge / discharge circuit in which a capacitor is connected in series to a parallel connection circuit of a resistor and a discharge diode is branched and connected.